How do a reseller modify a site?

One of my resellers wants to modify one of his sites account but there is no option to do that? Can somebody tell me how a reseller can modify his users account? All he wants to do is change the sites theme but there is no option to do this. I sent Eric an email about this weeks ago and no reply. Whats the use of hosting resellers who cant modify their own sites accounts. Thats nuts!!!!!!!!!!!!!!!!